An interesting solution to Y axis drift / shift

I've been plagued with Y axis drift / shift. On the occasional , specific print job, part way through the print would be off by a mm or two in the Y direction - front to back. So I'd get a stepped print. Maybe one step, maybe several.

I am printing a structural item so I upped the fill density to 80% from the default 40% in slic3r and the Y slippage was the worst I've ever seen. Not just a few mm but a centimetre at a time.... and many slips, one after the other. So I watched the print.

What was it? It's the infill causing reverberations, which cause the Y belt to oscillate wildly, and eventually jump a tooth on the motor. I've tightened the Y belt more, and I've dropped the gap-fill speed from 20 to 15 and the problem has gone away!

Thought I'd post this as I've not seen this suggested so far - slowing down the gap-fill density.

...not much to see = a belt vibrating wildly, then the occasional sound of a tooth slipping. Belt tightened and gap fill slowed and all is ok. I think either fix would have worked, but I did both at the same time and not only do the prints come out good now, the printer doesn't vibrate itself across the table!

Hmmmm - I've just watched it happen again. It's not belt tension. And I think it is related to gap fill, but more to infill "shake" - particularly with honeycombe infill.

I am running a print with 10% infill, honeycombe. it jumps/slips in teh same place each time.

I slowed infill down to 40 as a test. That indeed slowed the infill down... until... it gets to layers that have more detail on the edges - the head prints these details at full perimeter speeds, as they are indeed on the perimeter, but at the same time, it's adding to the honeycombe infill - this all gets hectic and the Y plate shakes to the point it "buzzes" and there is a "clunk" sound (I think that's the Y motor stalling) and the slip hgappens.

I'm going to stick with one object as it produces the fault reliably and fairly early on in the print. Many other prints of objects are fine.

I've got it to print 100% OK with zero infill.

I now tried rectingular - and it happened again. The infill doesn't seem to be the problem alone. It happens when there is a combination of infill and also other detailed layering.

In the video, you can see it's been going perfectly for all the layers that are just perimeters with infill. The infill type seems not to matter. It's when it gets to the layers that require infill and other layer detail, and it tries to draw so fast and small it shakes quite violently. Seemingly when it's filling in a tiny area.

In the video it fails and clunks (several times) at the 40 second mark. You can then see that it has slipped on the Y axis - (the slip is always in the same direction - always - i.e. it never slips so the print overlaps forwards, it's always backwards, if you see what I mean))

The printer has run fine for ages and only recently started doing this. I'm running at all the Slic3r default speeds apart from gap fill reduced from 20 to 15.

Additionally, a picture below. The items are photographed on the axis they print on the bed. The slipping starts as soon as it has to do infill AND the high density infill you see on three sides of the left object (I call it high density infill but it's not actually infill, it's the base of a hole)

Thanks...... - it's getting odder - I've been trying lots, and watching each time, and I've noticed - on this particular print, the printer most certainly speeds up just before the problem starts.. always in the same place.... huh? What would cause it to speed up? Must be in the Gcode?

at 36s it seems to speed up. Notice how much faster the next perimeter is.

I am now starting to wonder if that perimeter is perhaps the 1st that isn't technically an overhang and hence it speeds up. (it's an odd shape so most of the perimeters have at least some overhang).

I'm going to slowly ramp accell up until it breaks.

I'm suspecting now that I've just basically hit a print job that pushes my machine to it's limits and have got away with max accells of 9000 so far just mostly by luck - that and the machine has probably loosened up a bit.

Ok - played some more. My printer is MUCH happier running a slower Accel. I've bumped it from 500 to 1000 now (X and Y - X was ok but I figure it's better they match) and it's still good but much faster. The new accell figure has stopped all the violent jerking about and general roughness.

I'll slowly increase the accel and see where it leads me but this seems to be the culprit of my problems.

Like I said, I reckon as the machine loosened up, it became less tolerant of harsh jerky movements, which was exasperated by a particularly challenging specific print with lots of fast zig zag fill ins..

Update - doh! I found a setting in Slicer - slow print of layer is less than 30 seconds - which they are , until it speeds up. lol. Now I know why it speeds up!

Indeed. It's been working great for a while now. Got one small Y axis slip when I pushed my luck and dialled the speed up by 10%. Backed the accell off to 800 now and all seems good. Again, it was on a very tight zig zag .

I just printed out the nested birdhouse. All Slic3r had to do was tell the printer to make three passes per layer for each shell. But for some reason, it did the infill pass in lots of tiny segments, not one long pass from end to end. Weird.

Hello, I am having the same issue with the Y axis, I slowed the acceleration on both the X-Y and seemed to fix the Y drift. Now it drifts in the X. I turned the pots down on both the X and Y and for about half the print the X would stagger the layers then after the half way point it printed fine. I see you mentioned a setting in Slic3r to slow the print speed down, do you remember the setting you changed? Also, what do you have the DEFAULT_XYJERK set to?

I guess I would like to know what your Max acceleration, Acceleration and Jerk settings are set to.

I had this same issue with a Prusa I3. I decided to join the forum and stop fixing issues on my own and not giving back. So here's what I found. After looking at the Y axis motor... now my Y axis is under the bed. It's the bed axis not the extruders axis...

What I saw was that when I tightened the Y axis down hard the Y axis motor mount would tilt. It would tieter on the mount and the drive shaft would be angled slightly. The belt would pull the drive shaft and gear closer and make the shaft no longer 90 degrees from the belt direction.

This small 1-2 degrees of shift was causing the belt to slowly shift to the edge of the drive gear. The gear teath at that small angle would eventually skip a belt tooth.

So I had to straighten out the Y axis motor so that when the belt is tightened the motor doesn't move or tieter on the mount.

I hope this was descriptive enough to help others out there. This issue is a pain to solve.

BurtBurt:
I had the Problem with X and Y:
Tightened the X belt and all good there now.
Tightening Y did not help. Shortened the belt a bit, helped some but still not good.
I noticed the same thing when I was looking for the Y axis problem. Y stepper plate was loose and when I tightened the screws it did not firm up to my satisfaction.
Result: I epoxied the stepper to the back plate. Result of that; yet more minor improvement but still not good.
Looking at the Drive gear I determined it is a printed one. I noticed several of these parts in this very inexpensive machine were weak.
2 of them came in broken, and hollow. One of those was the X belt tensioning piece. Got replacements and built it.
I have never got a decent print off this thing.
Now to find a replacement Y Drive Gear. It's sloppy on the shaft.... AAArrrggghhhhhh.....

@ScRamjet: I also had the issue with the drift on the Y-Axis. I spent a lot of time in trying to fix it by tightening the belt which didn't help. Obviously the belt needs to be tight, but that wasn't the issue.

Then I noticed that the problem became even more apparent after I installed a printed geared-pulley on the idler. I finally fixed the issue for good, by installing an aluminum geared-pulleys on the idler that matches the gear on the stepper. I bought the matching aluminum geared idler pulley from Amazon - just search for "idler pulley" and make sure to get exactly matching dimensions, including the number of teeth to that of your stepper gear. I have never experienced the drift since then, regardless of the tension on the belt.

I know it's an older thread, but I just needed to add my thanks to Dodgey99. I have been fighting with my printer for the last two and a half months after doing some upgrades. In the process the Y offset became a problem for me, something I'd never run into before. I have tried multiple things with no luck. I finally figured it must have been something with the small areas creating a problem and after finding your post and turning down the acceleration it is currently printing the 6th attempt and it hasn't skipped once (the previous attempts had all been stopped by this point).

So thank you! I've been fighting with this specific problem since yesterday morning.